ad hominem Latin for “against the man,” this fallacy refers to the specific diversionary tactic of switching the argument from the issue at hand to the character of the other speaker. If you argue that a park in your community should not be renovated because the person supporting it was arrested during a domestic dispute, then you are guilty of ad hominem.

ad populum (bandwagon appeal) This fallacy occurs when evidence boils down to “everybody’s doing it, so it must be a good thing to do.”

You should vote to elect Rachel Johnson—she has a strong lead in the polls!

Polling higher does not necessarily make Senator Johnson the “best” candidate, only the most popular.

appeal to false authority This fallacy occurs when someone who has no expertise to speak on an issue is cited as an authority. A TV star, for instance, is not a medical expert, even though pharmaceutical advertisements often use celebrity endorsements.

argument A process of reasoned inquiry; a persuasive discourse resulting in a coherent and considered movement from a claim to a conclusion.

assumption See warrant.

backing In the Toulmin model, backing consists of further assurances or data without which the assumption lacks authority. For an example, see Toulmin model.

bandwagon appeal See ad populum.

begging the question A fallacy in which a claim is based on evidence or support that is in doubt. It “begs” a question whether the support itself is sound.

Giving students easy access to a wealth of facts and resources online allows them to develop critical thinking skills.

circular reasoning A fallacy in which the writer repeats the claim as a way to provide evidence.

You can’t give me a C; I’m an A student!

claim Also called an assertion or a proposition, a claim states the argument’s main idea or position. A claim differs from a topic or subject in that a claim has to be arguable.

claim of fact A claim of fact asserts that something is true or not true.

The number of suicides and homicides committed by teenagers, most often young men, has exploded in the last three decades . . .

—Anna Quindlen

claim of policy A claim of policy proposes a change.

Yet one solution continues to elude us, and that is ending the ignorance about mental health, and moving it from the margins of care and into the mainstream where it belongs.

—Anna Quindlen

claim of value A claim of value argues that something is good or bad, right or wrong.

There’s a plague on all our houses, and since it doesn’t announce itself with lumps or spots or protest marches, it has gone unremarked in the quiet suburbs and busy cities where it has been laying waste.

—Anna Quindlen

classical oration, the Five-part argument structure used by classical rhetoricians. The five parts are:

introduction (exordium) Introduces the reader to the subject under discussion.

narration (narratio) Provides factual information and background material on the subject at hand or establishes why the subject is a problem that needs addressing.

confirmation (confirmatio) Usually the major part of the text, the confirmation includes the proof needed to make the writer’s case.

refutation (refutatio) Addresses the counterargument. It is a bridge between the writer’s proof and conclusion.

conclusion (peroratio) Brings the essay to a satisfying close.

closed thesis A closed thesis is a statement of the main idea of the argument that also previews the major points the writer intends to make.

The three-dimensional characters, exciting plot, and complex themes of the Harry Potter series make them not only legendary children’s books but also enduring literary classics.

deduction Deduction is a logical process whereby one reaches a conclusion by starting with a general principle or universal truth (a major premise) and applying it to a specific case (a minor premise). The process of deduction is usually demonstrated in the form of a syllogism:

either/or (false dilemma) A fallacy in which the speaker presents two extreme options as the only possible choices.

Either we agree to higher taxes, or our grandchildren will be mired in debt.

fallacy See logical fallacy.

faulty analogy A fallacy that occurs when an analogy compares two things that are not comparable. For instance, to argue that because we put animals who are in irreversible pain out of their misery, we should do the same for people, asks the reader to ignore significant and profound differences between animals and people.

first-hand evidence Evidence based on something the writer knows, whether it’s from personal experience, observations, or general knowledge of events.

hasty generalization A fallacy in which a faulty conclusion is reached because of inadequate evidence.

Smoking isn’t bad for you; my great aunt smoked a pack a day and lived to be 90.

induction—From the Latin inducere, “to lead into”; a logical process whereby the writer reasons from particulars to universals, using specific cases in order to draw a conclusion, which is also called a generalization.

logical fallacy Logical fallacies are potential vulnerabilities or weaknesses in an argument. They often arise from a failure to make a logical connection between the claim and the evidence used to support it.

open thesis An open thesis is one that does not list all the points the writer intends to cover in an essay.

The popularity of the Harry Potter series demonstrates that simplicity trumps complexity when it comes to the taste of readers, both young and old.

post hoc ergo propter hoc This fallacy is Latin for “after which therefore because of which,” meaning that it is incorrect to always claim that something is a cause just because it happened earlier. One may loosely summarize this fallacy by saying that correlation does not imply causation.

We elected Johnson as president and look where it got us: hurricanes, floods, stock market crashes.

qualifier In the Toulmin model, the qualifier uses words like usually, probably, maybe, in most cases, and most likely to temper the claim, making it less absolute. For an example, see Toulmin model.

quantitative evidence Quantitative evidence includes things that can be measured, cited, counted, or otherwise represented in numbers—for instance, statistics, surveys, polls, census information.

rebuttal In the Toulmin model, a rebuttal gives voice to possible objections. For an example, see Toulmin model.

reservation In the Toulmin model, a reservation explains the terms and conditions necessitated by the qualifier. For an example, see Toulmin model.

Rogerian arguments Developed by psychiatrist Carl Rogers, Rogerian arguments are based on the assumption that having a full understanding of an opposing position is essential to responding to it persuasively and refuting it in a way that is accommodating rather than alienating.

second-hand evidence Evidence that is accessed through research, reading, and investigation. It includes factual and historical information, expert opinion, and quantitative data.

straw man A fallacy that occurs when a speaker chooses a deliberately poor or oversimplified example in order to ridicule and refute an idea.

Politician X proposes that we put astronauts on Mars in the next four years. Politician Y ridicules this proposal by saying that his opponent is looking for “little green men in outer space.”

syllogism A logical structure that uses the major premise and minor premise to reach a necessary conclusion.

Toulmin model An approach to analyzing and constructing arguments created by British philosopher Stephen Toulmin in his book The Uses of Argument (1958). The Toulmin model can be stated as a template:

Because (evidence as support), therefore (claim), since (warrant or assumption), on account of (backing), unless (reservation).

Because it is raining, therefore I should probably take my umbrella, since it will keep me dry on account of its waterproof material, unless, of course, there is a hole in it.

warrant In the Toulmin model, the warrant expresses the assumption necessarily shared by the speaker and the audience.